It is incontestable that wheelchairs have rendered handicapped persons and invalids mobile. However, such wheelchairs present a number of drawbacks, coming from the fact that the users can occupy only a sitting position which, moreover, is generally maintained for relatively long periods of time.
In the first place, this sitting position, the only one which can be adopted, does not allow re-adaptation to normal life and does not facilitate social contacts.
In the second place, this sitting position, maintained for generally long periods of time, is responsible for a physical deterioration loading to a loss of amplitude of angular mobility of the lower limbs, poor blood circulation, a marked slowing-down of the digestive and intestinal functions, fragility of the bones, etc. . .
In an attempt to overcome these drawbacks, different propositions have been made from a concept employing, on the chassis of the chair, an articulated structure comprising a backrest, a seat and a footrest. As a general rule, such an articulated structure is mounted on the seat by a horizontal front axle perpendicular to the vertical plane of symmetry of the chassis.
One of the propositions consists in interposing between the chassis and the structure a jack with electric motor which may be controlled to provoke raising or lowering of the articulated structure.
Another proposition has been to dispose between the structure and the chassis of the chair, on the one hand, at least one elastic compensator member and, on the other hand, at least one maneuvering assembly for performing a function of control and monitoring of the relative pivoting of the articulated structure and a function of geometrical locking of said structure, in lowered or raised position with respect to the chassis.
Such a proposition is illustrated by French Patent No. 2 529 456.
The technical solution thus proposed presents advantages of lightness, simplified construction and assembly, and enables the user to act, without considerable expenditure of physical energy, on the maneuvering assemblies for controlling and monitoring the raising and lowering strokes of the articulated structure on which he/she is resting.
In the concept of such a proposition, the maneuvering assemblies are designed so as to have available, in lowered position and in raised position, two states with certain geometrical locking, thus giving two extreme stable positions ensuring total safety for the user in order to avoid either an untimely elevation under the action of the elastic compensator, or a sudden lowering from the position of elevation or verticalization.
It must certainly be considered that such a proposition gives entire satisfaction to the users by the versatility of use that it gives them and by the freedom of movement that it offers.
Studios of operation, use and functional assessment of such elevator chairs, or verticalizers, have shown that, in certain cases, the users would have wished to be able to have, temporarily, a sort of assistance for alleviating or reducing the physical action which they must bear on the maneuvering assemblies. Such is the case when the user is suffering from a passing fatigue which is natural or consecutive to an operation or whose physical force has decreased slightly since the beginning of using such a wheelchair, without losing weight, to such an extent that the adjustment of the elastic compensator or replacement thereof become inoperative.
The problem is then raised of having available a partial and temporary motorized assistance, adaptable on a manually controlled elevator wheelchair or verticalizer or the above type, without converting such a wheelchair into complete-assistance equipment, such as those of the first proposition set forth hereinabove.
It may be considered that such a need may be satisfied by providing a motorization installation acting directly on the lateral control assemblies. However, experiments carried out in this sense show that such a modus operandi is virtually impossible and loads to ruptures either of the lateral assemblies directly or of their articulation members due to the high forces which must be applied to combat the multiplier effect which is attached by construction to the lateral assemblies.
It may also be considered that it suffices to act in association with the elastic compensator on the articulated structure and more particularly on the foundation, for example, by means of an articulated rod controlled by an appropriate driving member, In fact, such a proposition is not realistic either, as it does not take into account the necessity of neutralizing the upper and lower locking positions before initiating any control of pivoting of the articulated structure in raising movement or in lowering movement.
An additional difficulty to be solved concerns the desire to maintain in the wheelchair or verticalizer its nature of manual control and to provide possible means of motorized assistance which are adaptable, in removable manner, rapidly and easily, without their positioning disturbing the usual operational characteristics, and those of rolling stability, when stationery in lowered or raised position.
It is an object of the invention to respond to the demand thus perceived, by proposing technical means which overcome the problems set forth hereinabove, offering a practical, inexpensive, easily adaptable and dismountable solution, to render an elevator wheelchair or verticalizer possibly provided, or not, with a motorized assistance device.